Down feathers trap air close to the skin and help keep a bird warm.

The longer version

Down has a short soft shaft and loose barbs without hooking barbules, so instead of a flat vane it forms a light three-dimensional tangle. That tangle holds a layer of still air against the skin, and because still air conducts heat poorly, the bird's own warmth stays where it is needed.

Down sits underneath the contour feathers, which shield it from wind and wet. Water birds carry especially dense down and keep it dry with oil. Cold-weather clothing and bedding copy the same principle: loft, not weight, is what insulates, which is why wet down collapses and stops working.

Where this entry sits

Here you will find feathered trivia about flight, migration, nests, eggs, and the songs birds sing. Expect short surprising facts on penguins, owls, hummingbirds, and other familiar birds from gardens, forests, wetlands, and distant coastlines. The full list sits on the Birds page, where every entry is listed in order.